… | |
… | |
2070 | C<ev_async_sent> calls). |
2070 | C<ev_async_sent> calls). |
2071 | |
2071 | |
2072 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
2072 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
2073 | just the default loop. |
2073 | just the default loop. |
2074 | |
2074 | |
|
|
2075 | =head3 Queueing |
|
|
2076 | |
|
|
2077 | C<ev_async> does not support queueing of data in any way. The reason |
|
|
2078 | is that the author does not know of a simple (or any) algorithm for a |
|
|
2079 | multiple-writer-single-reader queue that works in all cases and doesn't |
|
|
2080 | need elaborate support such as pthreads. |
|
|
2081 | |
|
|
2082 | That means that if you want to queue data, you have to provide your own |
|
|
2083 | queue. But at least I can tell you would implement locking around your |
|
|
2084 | queue: |
|
|
2085 | |
|
|
2086 | =over 4 |
|
|
2087 | |
|
|
2088 | =item queueing from a signal handler context |
|
|
2089 | |
|
|
2090 | To implement race-free queueing, you simply add to the queue in the signal |
|
|
2091 | handler but you block the signal handler in the watcher callback. Here is an example that does that for |
|
|
2092 | some fictitiuous SIGUSR1 handler: |
|
|
2093 | |
|
|
2094 | static ev_async mysig; |
|
|
2095 | |
|
|
2096 | static void |
|
|
2097 | sigusr1_handler (void) |
|
|
2098 | { |
|
|
2099 | sometype data; |
|
|
2100 | |
|
|
2101 | // no locking etc. |
|
|
2102 | queue_put (data); |
|
|
2103 | ev_async_send (DEFAULT_ &mysig); |
|
|
2104 | } |
|
|
2105 | |
|
|
2106 | static void |
|
|
2107 | mysig_cb (EV_P_ ev_async *w, int revents) |
|
|
2108 | { |
|
|
2109 | sometype data; |
|
|
2110 | sigset_t block, prev; |
|
|
2111 | |
|
|
2112 | sigemptyset (&block); |
|
|
2113 | sigaddset (&block, SIGUSR1); |
|
|
2114 | sigprocmask (SIG_BLOCK, &block, &prev); |
|
|
2115 | |
|
|
2116 | while (queue_get (&data)) |
|
|
2117 | process (data); |
|
|
2118 | |
|
|
2119 | if (sigismember (&prev, SIGUSR1) |
|
|
2120 | sigprocmask (SIG_UNBLOCK, &block, 0); |
|
|
2121 | } |
|
|
2122 | |
|
|
2123 | (Note: pthreads in theory requires you to use C<pthread_setmask> |
|
|
2124 | instead of C<sigprocmask> when you use threads, but libev doesn't do it |
|
|
2125 | either...). |
|
|
2126 | |
|
|
2127 | =item queueing from a thread context |
|
|
2128 | |
|
|
2129 | The strategy for threads is different, as you cannot (easily) block |
|
|
2130 | threads but you can easily preempt them, so to queue safely you need to |
|
|
2131 | employ a traditional mutex lock, such as in this pthread example: |
|
|
2132 | |
|
|
2133 | static ev_async mysig; |
|
|
2134 | static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER; |
|
|
2135 | |
|
|
2136 | static void |
|
|
2137 | otherthread (void) |
|
|
2138 | { |
|
|
2139 | // only need to lock the actual queueing operation |
|
|
2140 | pthread_mutex_lock (&mymutex); |
|
|
2141 | queue_put (data); |
|
|
2142 | pthread_mutex_unlock (&mymutex); |
|
|
2143 | |
|
|
2144 | ev_async_send (DEFAULT_ &mysig); |
|
|
2145 | } |
|
|
2146 | |
|
|
2147 | static void |
|
|
2148 | mysig_cb (EV_P_ ev_async *w, int revents) |
|
|
2149 | { |
|
|
2150 | pthread_mutex_lock (&mymutex); |
|
|
2151 | |
|
|
2152 | while (queue_get (&data)) |
|
|
2153 | process (data); |
|
|
2154 | |
|
|
2155 | pthread_mutex_unlock (&mymutex); |
|
|
2156 | } |
|
|
2157 | |
|
|
2158 | =back |
|
|
2159 | |
|
|
2160 | |
2075 | =head3 Watcher-Specific Functions and Data Members |
2161 | =head3 Watcher-Specific Functions and Data Members |
2076 | |
2162 | |
2077 | =over 4 |
2163 | =over 4 |
2078 | |
2164 | |
2079 | =item ev_async_init (ev_async *, callback) |
2165 | =item ev_async_init (ev_async *, callback) |
… | |
… | |
2607 | |
2693 | |
2608 | If defined to be C<1>, libev will compile in support for the Linux inotify |
2694 | If defined to be C<1>, libev will compile in support for the Linux inotify |
2609 | interface to speed up C<ev_stat> watchers. Its actual availability will |
2695 | interface to speed up C<ev_stat> watchers. Its actual availability will |
2610 | be detected at runtime. |
2696 | be detected at runtime. |
2611 | |
2697 | |
|
|
2698 | =item EV_ATOMIC_T |
|
|
2699 | |
|
|
2700 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
|
|
2701 | access is atomic with respect to other threads or signal contexts. No such |
|
|
2702 | type is easily found in the C language, so you can provide your own type |
|
|
2703 | that you know is safe for your purposes. It is used both for signal handler "locking" |
|
|
2704 | as well as for signal and thread safety in C<ev_async> watchers. |
|
|
2705 | |
|
|
2706 | In the absense of this define, libev will use C<sig_atomic_t volatile> |
|
|
2707 | (from F<signal.h>), which is usually good enough on most platforms. |
|
|
2708 | |
2612 | =item EV_H |
2709 | =item EV_H |
2613 | |
2710 | |
2614 | The name of the F<ev.h> header file used to include it. The default if |
2711 | The name of the F<ev.h> header file used to include it. The default if |
2615 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
2712 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
2616 | used to virtually rename the F<ev.h> header file in case of conflicts. |
2713 | used to virtually rename the F<ev.h> header file in case of conflicts. |
… | |
… | |
2681 | defined to be C<0>, then they are not. |
2778 | defined to be C<0>, then they are not. |
2682 | |
2779 | |
2683 | =item EV_FORK_ENABLE |
2780 | =item EV_FORK_ENABLE |
2684 | |
2781 | |
2685 | If undefined or defined to be C<1>, then fork watchers are supported. If |
2782 | If undefined or defined to be C<1>, then fork watchers are supported. If |
|
|
2783 | defined to be C<0>, then they are not. |
|
|
2784 | |
|
|
2785 | =item EV_ASYNC_ENABLE |
|
|
2786 | |
|
|
2787 | If undefined or defined to be C<1>, then async watchers are supported. If |
2686 | defined to be C<0>, then they are not. |
2788 | defined to be C<0>, then they are not. |
2687 | |
2789 | |
2688 | =item EV_MINIMAL |
2790 | =item EV_MINIMAL |
2689 | |
2791 | |
2690 | If you need to shave off some kilobytes of code at the expense of some |
2792 | If you need to shave off some kilobytes of code at the expense of some |
… | |
… | |
2811 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
2913 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
2812 | |
2914 | |
2813 | That means that changing a timer costs less than removing/adding them |
2915 | That means that changing a timer costs less than removing/adding them |
2814 | as only the relative motion in the event queue has to be paid for. |
2916 | as only the relative motion in the event queue has to be paid for. |
2815 | |
2917 | |
2816 | =item Starting io/check/prepare/idle/signal/child watchers: O(1) |
2918 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
2817 | |
2919 | |
2818 | These just add the watcher into an array or at the head of a list. |
2920 | These just add the watcher into an array or at the head of a list. |
2819 | |
2921 | |
2820 | =item Stopping check/prepare/idle watchers: O(1) |
2922 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
2821 | |
2923 | |
2822 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
2924 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
2823 | |
2925 | |
2824 | These watchers are stored in lists then need to be walked to find the |
2926 | These watchers are stored in lists then need to be walked to find the |
2825 | correct watcher to remove. The lists are usually short (you don't usually |
2927 | correct watcher to remove. The lists are usually short (you don't usually |
… | |
… | |
2841 | =item Priority handling: O(number_of_priorities) |
2943 | =item Priority handling: O(number_of_priorities) |
2842 | |
2944 | |
2843 | Priorities are implemented by allocating some space for each |
2945 | Priorities are implemented by allocating some space for each |
2844 | priority. When doing priority-based operations, libev usually has to |
2946 | priority. When doing priority-based operations, libev usually has to |
2845 | linearly search all the priorities, but starting/stopping and activating |
2947 | linearly search all the priorities, but starting/stopping and activating |
2846 | watchers becomes O(1) w.r.t. prioritiy handling. |
2948 | watchers becomes O(1) w.r.t. priority handling. |
|
|
2949 | |
|
|
2950 | =item Sending an ev_async: O(1) |
|
|
2951 | |
|
|
2952 | =item Processing ev_async_send: O(number_of_async_watchers) |
|
|
2953 | |
|
|
2954 | =item Processing signals: O(max_signal_number) |
|
|
2955 | |
|
|
2956 | Sending involves a syscall I<iff> there were no other C<ev_async_send> |
|
|
2957 | calls in the current loop iteration. Checking for async and signal events |
|
|
2958 | involves iterating over all running async watchers or all signal numbers. |
2847 | |
2959 | |
2848 | =back |
2960 | =back |
2849 | |
2961 | |
2850 | |
2962 | |
2851 | =head1 Win32 platform limitations and workarounds |
2963 | =head1 Win32 platform limitations and workarounds |